Mining of sulfur by liquefaction of the sulfur



M. H. PARKS 2,808,247

MINxNG oF SULFUR BY LIQUEFAUTIUN oF THE SULFUR Oct. 1, 1957 Filed Sept. 26, 1956 Compressed Air Molten Sulfur Hof Wafer INVENTOR. Mercer H. Parks A TTOR MINING OF SULFUR BY LIQUEFACTION OF THE SULFUR Mercer H. Parks, Houston, Tex., assigner to Humble Oil & Refining Company The present invention is directed to a method of mining sulfur. More particularly, the invention is concerned with the mining of sulfur from subsurface formations without causing subsidence of overlying formations. In its more specific aspects, the invention is directed to the mining of sulfur under controlled conditions whereby the pressure and volume of the ore body which contains the sulfur remains substantially under a constant pressure and at a substantially constant volume.

The present invention may be briefly described as a method for mining sulfur from a sub-surface earth formation containing a sulfur ore body by liquefaction of the sulfur. The invention specifically contemplates that all or major portions of the ore body will be heated as uniformly as possible to a temperature below the incipient melting point of the sulfur in the ore body. Thereafter, the temperature of the heated ore body is increased at least adjacent a well penetrating the ore body to a temperature suicient to melt the sulfur in the region of or adjacent said well. Thereafter, the melted sulfur is produced through the well.

In accordance with the present invention the pressure and volume of the heated ore body is maintained substantially constant while producing sulfur from the ore body. This may be accomplished by injecting into the heated ore body a suiiicient amount of water at an elevated temperature to liquefy or melt the sulfur in the heated ore body adjacent the production well and withdrawing from the heated ore body only a sucient amount of fluid including melted sulfur and mine water sufcient to compensate for the amount of heated water injected into the ore body.

It is contemplated that the heated ore body will be substantially completely heated to a temperature below the incipient melting point of the sulfur in the ore body; for example, at a temperature below about 240 F. may be satisfactory. The temperature of 238 F. is exemplary of temperatures contemplated in the practice of the present invention. In heating the ore body to a temperature below the incipient melting point of the sulfur in the ore body, the heated water may be injected into the sulfur-bearing ore body incrementally. For example, the hottest water at a temperature of about 240 F. may be introduced into the upper part of the sulfur bearing formation or ore body and thereafter other increments of heated water at decreasing temperatures may be in-l troduced below the upper layer of water introduced into the ore body such that the ore body is maintained at a temperature below the incipient melting point of the sulfur in the ore body.

In accordance with the present invention, it is contemplated that sulfur will normally be produced from the same wells used for water injection but may be produced from one well while heated mine water is introduced into another well; It is further contemplated that the rst wells may be up formation from 'the second wells which are down formation from the rst wells such that the sulfur progressively melted from the ore body and not atent which may suitably be termed 29a and to cement the v ICC mud, oil, water less saline than formation water, or it may be gas under pressure.

The present invention will be further illustrated by reference to the drawing in which the single figure illustrates a preferred mode. Referring now to the drawing, numeral 11 designates -a sulfur ore body which has a p0rous, barren cap rock 12 overlying same and above which are sedimentary deposits 13, 14, 15 and16. The sulfur ore body may suitably .be located beneath a body of water, such as, for example, in the Gulf of Mexico, orl

suitably may be beneath the Coastal plains, such as inr Texas or Louisiana. formations 13 to 16 and to penetrate the porous, barren cap 12 is a borehole 17 in which is arranged a casing string 18 which is suitably cemented in place by cement 19. The casing 18 is penetrated to form perforations 20 into the porous, barren cap 12. Arranged within the casing string 18 is a water string 21 which extends into the borehole 22 of reduced diameter in the sulfur body 11. The annulus 23 between the water casing string 18 and the water string 21 is suitably closed by a packer 24 of a type .t

which will permit relative `movement of water string 21 to casing string 18 Without resetting or damaging the` packer.

Arranged within the Water string 21 is an inner pipe or sulfur tubing string 25 and arranged within the inner pipe string 25 is `a second inner pipe string 26 which suitably may be termed an air string. Water may be introduced down the annulus 27 between the string 25 and the water string 21 and sulfur may be produced upwardly through the annulus 28 between the string 25 and the string 26 while air may be introduced downwardly throughthe string 26. The air string 26 is run in wells A only after the formation has been heated uniformly as noted before and sulfur production is to begin. It will be run in wells B if air or gas lift is used to remove water from the formation as described.

The water string 21 is perforated by perforations 29 throughout its traverse of the sulfur ore body i1 and the sulfur string 25 is also provided with pcrforations 30 adequate to pass required volume of water above packer 31 between sulfur and water strings 25 and 21.

In providing a well of thenature described, it is desirable to seal the casing string 18 in the weil bore 17 and to cement the water string 21 into the ore body 11 but not cement it to the casing string 18. In order to achieve this end, prior to running in the pipe strings 25 and 26, the lower portion of the water string 21 is sealed off by means of a drillable packer which may suitably be a cement plug, not shown, to isolate the uppermost of the peiforations 29 from the lowermost of the perforaticns and to squeeze cement through these upper perforations that the perforations 20 and perforations 29 Vand 29a and Patented Oct. 1, 1957V Drilled through the sedimentary theP perforations 30 maybe formed in the several strings at the well head prior to placing the particular pipe string in the well or may beV formed by gun perforating bylowering a perforator down through" theA respective strings prior to lowering the last stringtherethrough; any event, it is contemplated that the severalV perforationsmay beVV provided.

The foregoing description refers to a` rst welll A which' may be drilled up formation in thesulfur orebody and a-second`well, which may be termed well B; may be subsequently drilled to penetratethe sulfur ore body down formationfrom the well A. The` same'- procedure andv thessame elements are providedforwell B and itA is unnecessary to designate the several elements` by diffrent numerals. Accordingly, wellA andwelliB have identical partsnumberedlidentically. These' Wells are typical and it'is contemplated that aY number of each. wouldy be required vinthe 'proposedoperationz In practicing the present invention' with wells A' and wells B, asshownA in the drawing,.the' firstr step to be employed' if a porous, barren cap, such as 12`,.is above' thefsulfurV ore body 11, is-toill` the porous barren cap 12x with a suitablefluid which will prevent migrationof theheated mine water up into, the porous, barren cap. T othisend, the suitable tiuid, suclr as has been described, is-forced down the annnlus 23 and through the perforations 2t) to iill the porous, barren cap. withV duid and top revent migration of mine water' into the barren cap.V Asstated, this duid may'suitably be'mud', oil, water, or gas. This fluidv under pressure' also servesV to prevent subsidence of the overlying strata or formations 13` to 16`4 and to prevent collapse as the sulfur is mined from the-ore'body 11.

Heated mine water is' then' flowed down the annulus 277 at a temperature suflicient to heat the'wholecof the ore body 11 to a temperature below the incipient melting point of the sulfur in theV ore body 11`. In short, all or' the major portion of ore' body` 11L is heated to a temperature below the melting point' of'sulfur, such that byraisingthe temperature of portions. of the heatedore bodyV adjacent the well, it is then possible to liquefy or melt theV heated sulfur by raising the tenlperature` of the ore body Vonly slightly. Thus a relativelyy smallY quantity of heat will melt arelatively large quantity of sulfur in` a very short time.

Oncev the heated ore body is heated to a temperature asK has been described, the next step is the liquefaction of-tl'ieV sulfur adjacent or in the region of either wells A or B and to produce the sulfur from the annulus 28n using air or gas lift by introducing air or gas down through the inner pipe string` 26.

As has been described briefly, the rst step of the present invention is to ll the pores of the porous, barren cap rock with a uid, such as has been indicated, to prevent convection of hot mine water into the formation 12. This introduction of a uid, such as mud or water less saline than formation water, is usually through the wells A which are up` structure from the wells B and is through the annulus 2.3'and perforations 20. The volume and'temperature of this injectedv uid are carefully controlled and a radioacitve tracer element, such as tritrium, having a half life of l2 years may be introduced therewith in order to follow the travel of the fluid. It is desirable to follow the travel of the huid in the porous,

barren cap such that the fluid travels toward all of the.

surrounding wells of which well B may be representative.

In order to maintain this travel, it may be desirable to bleed finid from weli'B, for example through theannulus 28 to cause a differentialpressure between wells A and B to induce movement of fluid` fromfwell Ato well- B. Of course, it is desirable simultaneously to maintain reservoir pressure by a careful controlv of the injection fuid and control of the'withdrawn fluid. Travel,

as correlatedfto` injection and withdrawal, can suitably.

be determined by testing the withdrawn water or uid i from well Bv for the" radioactive' tracer elementV and by determining its temperature.

This operation is continued until the porous, barren cap rock is satisfactorily filled or until it has been filled sufficiently to accomplish the end of preventing migration of heated mine water.

Thereafter the injection of hot water begins at wells A.4 The sulfur tubing string 2S maybe set so that the packer 31 'in wells A exposes only a few feet of perforations 29 near the top' of' the sulfurore: body 11. This water may be firstk injected atf 315 F. or higher but a careful control thereof is desirable such that little, if any, of the sulfur in the body 1'1 is melted. As the temperature of the ore. body- 1.1.risesrto approximately 238 or 240 F. or a suitable point below the sulfur melting point in the upper part of the sulfur ore body 11, the packer 31 is lowered and the Water temperature may be decreased slightly with the volume ofthe water correspondingly increased t'o deposit a layer of water below the layer of ywater at 238V F.; for example, the second layer ofl water may be below 238 F. followed by a third layer of water and other layers of water at progressively lower temperatures as may be desired. As the ore body 11 becomes progressively heated, some of theV wells B may be made injection wells for injection of hot water to aid in the heatingy of the ore body 11 in the region of the wells Bl As an alternate to heating by the creation of layers of progressively cooler water as the lower parts of .the formation are lled, it is contemplated that a simplification might accomplish the purpose of preheating simply by injecting water between 240 F. and 315'o F. through the lower perforations of water string 21', such as it would'beinjected for regular Frasch mining, except that care would be exercised to prevent the melting ofl appreciable amounts ofsulfur.

When. hot water injection is started at wells A, bleeding of water is started at wells B through the annulus 27 or water stringZl, alone,.at a rate not only to maintain the pressure within the reservoir 11 but to. maintain its volume substantially constant taking into consideration the expansion characteristics-of all reservoir material and the physicalchanges in the rock as it becomes depleted of its sulfur. Thus, a suicient amountof hot water is injected-to. compensate: for the amounts of bleedwater and. sul-fur, if any, withdrawn.

It is possible. also toV be injecting uidinto the porous, barren cap 12. simultaneously with the heating of the sulfur ore body 11 provided, of course, that the amount of fluid injected into barrencap 12. and itscourse have been determined such .that convection does not cause the hot water injected to heat the ore body`11 to migrate into the cap 12.v

It is recognized that the sulfur inthe ore body 11 supplies a'considerable portion. of the strength. of the' cap rock 12 to resist the crushingfof the overlying strata or. formationslZto 16;H In the mining of sulfur, subsidence is a problem. In accordance withthe present invention the sulfurv isprevented frornmelting` until it isY desiredfto produce the sulfur suchl that` it`V may be produced ina volumeisuicient such that the-volumeV as well as the pressure in the ore body 11A may be maintained substantially constant in order to prevent overloading of the' caprock orl barren cap 12 at any stage of. the heating.` orofthe sulfur melting. While the. volume of the'waterand sulfur removed from Wellsk A or'B' may be followed to determine the maintenance of the', volume inthe formation, another method of followingrthe maintenance of pressure and volume of the formations is by hanging the waterstring 21 in the top part of the sulfln ore body 11 by means of thesqueeze cementv 32. The weight of the pipe; in the string 21 may be. set ldown on this cement 32 andthe remainder of the' weight/may be carried'by a; weight indicator device at the toprof the hole which, by registering an increased load, will in-v dicate incipient failure through melting of the sulfur from around the cement plug with slippage of the casing 21 through the packer 24. Alternately, the movement of the casing 21 may be noted at the surface through levelling same with respect to a xed elevation. Differential movement of strings 18 and 21 may also be a control for the maintenance of the pressure and volume of the sulfur ore body 11 and a porous, barren cap 12.

After the sulfur ore body 11 has been substantially completely heated to a temperature about or below 240? F., the air or gas lines 26 may be run into the well and a temperature of the injected water increased to about 315 F. with the result that the sulfur in the ore body 11, which is below incipient melting point, may be supplied with the necessary heat input for fusion and melting to take place with the employment of a relatively small amount of hot water per ton of sulfur produced. In short, the wells A and B may then be produced under control by controlling the volume of fluids in the reservoir constant by controlling the bleed water with respect to the water injected and the sulfur removed, other conditions, such as temperatures and pressures alsobeing controlled. Thus, in the present invention it is essential that the reservoir configuration be maintained substantially unchanged through maintenance of equilibrium within it and thus prevent subsidence with the attendant slippage of formations which destroys wells and interrupts production by subsurface and surface dislocations.

It is contemplated in the practice of the present invention that if the sulfur becomes depleted from the highest point in a formation or strata of a sulfur ore body that that portion of the porous, barren cap and its overlying strata may be caused to collapse by deliberately bleeding through a well B to reduce volume and thereby force the fluids within the depleted portion of the sulfur ore bodies out and down formation to heat that portion of the formation such as is adjacent to a Well B.

In the practice of the present invention where the porous, barren cap rock is filled with a substance to prevent ingress of hot water while the ore body is heated to a temperature below the incipient melting point of the sulfur in the ore body, it may be desirable to employ water of lesser density than that in the formation. For example, sea water having a density of slightly over 1.0 might be employed to displace cap rock water of a density of as much as 1.1 to 1.2, reducing the dilerence in cap rock water and heated sea water having a density of from about 0.95 to 0.91 used to heat the sulfur ore body. In other words, by selecting the density of the water employed to till the porous, barren cap rock, the tendency ofthe water to migrate into the porous, barren cap rock may be controlled.

The present invention is of considerable importance and utility in that the number of wells employed and the attendant operating equipment is substantially reduced. The sulfur is substantially completely mined from the ore body with a minimum amount of water and heat input and subsidence of overlying strata or formations is substantially completely eliminated.

The nature and objects of the present invention having been completely described and illustrated, what I wish to claim as new and useful and to secure by Letters Patent is:

l. A method for mining sulfur from a subsurface earth formation containing a sulfur ore body by liquefaction of the sulfur which comprises introducing into said ore body a sutlicient amount of heated Water at a suicient temperature to heat said ore body and to raise the temperature of the ore body to a temperature below the incipient melting point of sulfur in said ore body, then raising further the temperature of the heated ore body at least adjacent a well penetrating said ore body a sufcient amount to melt the sulfur in said heated ore body adjacent said well, and then producing melted sulfur and water through said well, the pressure and volume of said heated ore body beingmaintained substantially constant by controlled injection of heated water into the heated ore body under pressure and at a rate sufficient to compensate for the amount of melted sulfur and water produced from the heated ore body, the heated water injected into the heated ore body by controlled injec. tion being at 'a temperature su'icient to raise the temperature of the heated ore body to melt the sulfur.

2. A method for mining sulfur from a subsurface earth formation containing a sulfur ore body by liquefaction of the sulfur which comprises heating said sulfur ore body to a temperature below the incipient melting point of the sulfur in said ore body, increasing the temperature of the heated ore body adjacent a well penetrating said ore body to a temperature sufficient to melt the sulfur in said ore body adjacent said well, and then producing melted sulfur and water through said Well, the pressure and volume of said heated ore body being maintained substantially constant by controlled injection of heated water into the heated ore body under pressure and at a rate suiicient to compensate for the amount of melted sulfur and water produced from the heated ore body, the heated water injected into the heated ore body by controlled injection being at a temperature suflicient to raise the temperature of the heated ore body to melt the sulfur.

3. A method in accordance with claim 2 in which the ore body is heated to a temperature below approximately 240 F.

4. A method in accordance with claim 2 in which the ore body is heated to a temperature below the incipient melting point of the sulfur in the ore body by injection of heated water through a irst well penetrating said ore body and melted sulfur is produced through a second well penetrating said ore body down formation from the irst well.

5. A method in accordance with claim 2 in which the sulfur ore body is heated to .a temperature below the incipient melting point of sulfur by injecting in sequence increments of heated water at progressively decreasing temperatures to maintain the temperature of the ore body below the melting point of sulfur.

6. A method in accordance with claim 5 in which the increments of heated water of decreased temperature are injected into said ore body below increments of heated water at a higher temperature.

References Cited in the tile of this patent UNITED STATES PATENTS 1,719,981 Judson July 9, 1929 

1. A METHOD FOR MINING SULFUR FROM A SUBSURFACE EARTH FORMATION CONTAINIG A SULFUR ORE BODY BY LIQUEFACTION OF THE SULFUR WHICH COMPRISES INTRODUCING INTO SAID ORE BODY A SUFFICIENT AMOUNT OF HEATED WATER AT A SUFFICIENT TEMPERATURE TO HEAT SAID ORE BODY AND TO RAISE THE TEMPERATURE OF THE ORE BODY TO A TEMPERATURE BELOW THE INCIPIENT MELTING POINT OF SULFUR IN SAID ORE BODY, THEN RAISING FURTHER THE TEMPERATURE OF THE HEATED ORE BODY AT LEAST ADJACENT A WELL PENETRATING SAID ORE BODY A SUFFICIENT AMOUNT TO MELT THE SULFUR IN SAID HEATED ORE BODY ADJACENT SAID WELL, AND THEN PRODUCING MELTED SULFUR AND WATER THROUGH SAID WELL, THE PRESSURE AND VOLUME OF SAID HEATED ORE BODY BEING MAINTAINED SUBSTANTIALLY CONSTANT BY CONTROLLED INJECTION OF HEATED WATER INTO THE HEATED ORE BODY UNDER PRESSURE AND AT A RATE SUFFICIENT TO COMPENSATE FOR THE AMOUNT OF MELTED SULFUR AND WATER PRODUCED FROM THE HEATED ORE BODY, THE HEATED WATER INJECTED INTO THE HEATED ORE BODY BY CONTROLLED INJECTION BEING AT A TEMPERATURE SUFFICIENT TO RAISE THE TEMPERATURE OF THE HEATED ORE BODY TO MELT THE SULFUR. 